Sophorolipids are known as a class of biosurfactants of biological origin. Sophorolipids are obtained by fermentation of a yeast (Non-Patent Literature 1). Sophorolipids are easily produced by a simple process involving, for example, inoculation of a yeast in liquid medium supplemented with a carbon source such as a sugar (e.g., glucose) and a vegetable oil or fat, and culture with aeration and agitation at moderate temperature under moderate pressure. Sophorolipids can be produced in large quantities, are highly safe and has other advantages. Due to these features, sophorolipids are used in combination with a physiologically active substance and are applied to various fields including the detergent, pharmaceutical, cosmetics, and food sectors (Patent Literature 1).
A physiologically active substance, however, even when orally administered in combination with a sophorolipid, is often degraded by digestive juices such as the saliva, gastric juice and intestinal juice, or its bioavailability through intestinal absorption is not always meet the requirements.